Combustor and cooling means therefor



Sept. 15, 1953 R. w. ABBOTT $651,912

COMBUSTOR AND COOLING MEANS THEREFOR Filed Oct. 31, 1950 2 Sheets-Sheetl '0 O G C) Q Q 0 C) C) Inventor: iRCH W- bg )Q/fl o His Attorne g.

Sept. 15, 1953 R. w. ABBOTT 2,651,912

COMBUSTOR AND COOLING MEANS THEREFOR Filed Oct. 51, 1950 2 Sheets-Sheet2 /llV AiV Inventor: R05 W. Abbott,

H is Attorne g.

Patented Sept. 15, 1953 CODIBUSTOR AND COOLING MEANS THEREFOR Roy W.Abbott, Schenectady, N. Y., assignor to General Electric Company, acorporation of New York Application October 31, 1950, Serial No. 193,100

3 Claims. 1

This invention relates to apparatus for the combustion of fluid fuels.More particularly, it relates to an improved combustion chamber linerhaving new and novel means for cooling such liner.

An object of this invention is to provide combustion apparatus for fluidfuels which affords improved combustion eificiency.

Another object of the present invention is to provide combustionapparatus which is characterized by improved liner wall cooling.

A further object of the invention is to provide a combustion chamberliner i which hot spots are substantially eliminated.

Another object of this invention is to provide combustion apparatus inwhich the cooling area per louver is substantially increased.

Another object of the invention is to provide a combustor in which theexit gases are characterized by improved temperature uniformly acrossthe chamber.

A still further object of the present invention is to provide combustionapparatus in which the liner is cooled by substantiallycircumferentially flowing gas.

Other objects will become apparent from a consideration of the followingdescription and the drawing in which Fig. 1 shows in partiallongitudinal cross-section a combustor embodying the present invention;Fig. 2 is a detail perspective view of the louver structure; Fig. 3 is acrosssectional view of a portion of the liner of Fig. 1 taken in thedirection 3-3 and Fig. 4 is a longitudinal cross-sectional view of aportion of the liner.

It has been found that a combustor for fluid fuels which ischaracterized by improved liner cooling may be very readily provided.

More particularly, it has been found that such a combustion apparatusmay be realized by providing a plurality of deflecting louvers somounted in longitudinally disposed slots in the liner that airintroduced into the slots is spread tangentially and circumferentiallyover the inner surface of the liner.

Heretofore, a number of methods of cooling the inner surfaces ofoombustor liners have been proposed. One such method introduces the airin a downstream direction through louvers provided by making U-shapedcuts in the liner wall and bending inwardly the tongue so formed. Whilesuch a method of film cooling is efficient insofar as the areas actuallycontacted by the coolant are concerned, the latter has a tendency torapidly disperse and become entrained in the combustion gases.Additionally, the provision of sufficient of such louvers to effectivelycool the entire liner wall and eliminate all hot spots has a tendency tophysically weaken the liner wall.

By the present invention there is provided a means of effectivelycooling the entir surface of a combustor liner by metering air throughlongitudinally disposed slots and associated louvers so that the coolantis swept tangentially and circumferentially over the inner circumferenceof the liner.

The present method of liner wall cooling reduces to a minimum theconduction and connection of heat from the high temperature flames tothe wall. It offers the further advantage of reusing this cooling airfor combustion and dilution to further augment that introduced throughthe liner hoies for this purpose. The improved cooling also makespossible a more uniform exhaust gas temperature and high combustionefficiency.

For a more complete understanding of the present invention, reference ismade to the drawing. In Fig. 1 is shown a typical combustor embodyingthe present improvement. Mounted within the outer combustor shell I isliner 2 which is held in spaced relationship with the shell by means ofstruts such as 3 to form a plenum chamber Air is fed to plenum chamber 5through the end 5 of the combustor from a source of supply not shown.The only requirement for the air supply in space 41 is that it havesubstantially no downstream velocity component, such condition beingreadily attained by adjustment of feed pressures and directions andchamber size which are well known to those skilled in the art. Fuel isintroduced into the combustor through a nozzle which introduces aconical spray of fuel into the liner. Preferably, though notnecessarily, the nozzle is of the so-called duplex type which delivers amultiple conical spray of fluid. Such a nozzle is described inapplication Serial No. 622,604, filed October 16, 1945, now Patent2,590,853, assigned to the same assignee as the present invention.Ignition of the fuel is accomplished by means of spark device I mountedin the wall of the combustor.

A plurality of slots 8 is provided in liner 2 extending from a positionnear the nozzle at the closed end of the liner downstream beyond thedilution portion of the liner. A plurality of T- shaped louvers 9 ismounted in slots 8 in inverse fashion to allow air to be metered throughslot 8 and into the liner chamber between the louvers and liner wall,and arranged end-to-end with a slight space between each to provide forexpansion. Louvers 9 may be made in any desired manner which will occurto those skilled in the art. In Fig. 2 is shown a louver structure whichhas been found very satisfactory in actual use. Horizontal piece it] isfixed as by welding l l to upright piece 12. Piece I2 is also notched asat l3 to receive bridge M which rests in the notch I3 perpendicular topart 12. The height of bridge Hi and the depth of notch l3 are soadjusted that when the louver is placed in slot 8 as shown in thedrawing and the bridge fixed in the notch, the bridge will rest on theouter wall of liner 2 and hold the louver in proper relationship withthe slot 8 and liner wall 2. To provide or compensat for differentialexpansion between the liner wall and the louver or deflectingarrangement, the latter is made in a number of sections 9 which arewelded to the liner as shown in Fig. 2 at 15. The other end is fitted tothe adjacent louver section for slight longitudinal movement by means ofpins i6 which fit loosely into holes drilled in the horizontal portionof the louver. In a chamber about four and one-half inches in diameter,end play between louver sections of about one-sixty-fourth inch isadequate.

The louvers and combustor liner may be constructed of any heat resistantmetal. Preferred are stainless steel, calorized or stainless steel cladcopper and Inconel, an alloy having 12%-14% Cr, 78%-80% Ni, and 6%8% Fe.

The space between the upri ht portion of the louver or deflecting meansand the liner wall and the space between the horizontally disposedportion of the louver will vary with the size of the combustor. Thewidth of the space between the edge of slot 8 and the louver upright mayvary from 0.014: to 0.03 and preferably about 0.0055 of the innerdiameter of the liner. The distance between the liner and the horizontalpart of the louver may vary from about 0.003 to 0.01 of the linerdiameter and preferably is about 0.0055 of the liner diameter.

The number of slots found most preferable in the present combustor inorder to provide the necessary cooling is six. However, from five toseven equidistant slots will produce almost as good results. Less thanfive slots provides inade quate cooling while more than seven producestoo much interference and turbulence between air flow from adjacentslots.

Rows of combustion and dilution air inlet holes I? are provided betweenthe rows of louvers. It has been found that for most efficientoperation, the size of these holes should range from about 0.01 to 0.12of the inner diameter of the liner. The preferred hole size is 0.11 thatof the liner diameter.

In operation, fluid fuel is sprayed through nozzle 6 in a conical sprayas shown. At the same time air pumped into plenum chamber 4 enters slots8 and is metered between the louver and liner wall into the linerchamber. That part of the air introduced through louvers locatedupstream of holes ll describes a path similar to that shown by thearrows I 8 in Fig. 3. As shown, entrant air sweeps circumferentiallyover the inner liner surface, being held against the wall by centrifugalforce. As the air from two adjacent slots meets, the air streams flowradially inward toward the center of the chamber as shown. At a pointnear the center of the chamber the streams reverse and flow radiallyoutward toward the low pressure area under the louver from which theparticular stream emanated.

Combined with the above air stream flow is that shown in Fig. 4. Herethe air entering air inlet hole I! nearest the nozzle is shown asflowing radially inward toward the center of the chamber where part ofit turns and proceeds toward the nozzle as typified by arrows l9 and 20,sweeping up any unburned fuel particles. The other part of the airstream proceeds downstream and forms a tore as indicated by arrow 2|.Air which is entrant through other holes downstream describes paths asshown. A more detailed description of the formation of torous regionswithin the combustion chamber will be found in application Serial No.750,015, filed May 23, 1947, now Patent 2,601,000, and assigned to thesame assignee as the present application.

The first air inlet hole I1, it will be noted, is located some distancedownstream from the nozzle. This distance, about one and one-half timesthe inner chamber diameter, is maintained in order that such entrant airwill not chill the primary combustion area which extends to the firstinlet hole H, but will be preheated before it reaches that region tocombine with air from the louvers in the primary combustion zone. Sincethe primary air obtained from the louvers is also heated by convectionand radiation, the temperature of the gases in the primary combustionregion is maintained at a higher temperature than in other combustors.This makes possible improved efficiency and stable combustion with areduced oxygen volumetric concentration as low as 15% instead of theusual 21% found in air.

The primary combustion region or zone is one of gas preheating, highenergy mixing and calm burning. That region just downstream of the firstair inlet holes is called the secondary combustion zone and is one ofmore violent mixing and burning. This zone covers roughly the middlethird of the combustor where air issuing from the louvers is entrainedin that issuing from the air inlet holes as it reaches the holes andproduces a violent torous region of burning gases. The last third of thecombustor comprises a diluting zone wherein the burned gases are dilutedwith air from the louvers and holes and reduced to a temperature whichwill not damage any mechanism such as turbine blades which are to bedriven by the gases.

The present method of wall cooling and additional utilization of thecooling air for combustion and diluting makes possible the eliminationof hot spots in the liner and chamber and produces a uniform skintemperature. With an average exhaust temperature of 1500 F., the exhaustgas temperature variation across the chamber is not over F. Under thesame conditions the liner wall temperature ranges from 850 F. to 950 F.

The pressure drop in the present combustor is about 2.3 per cent. Thecombustion efficiency ranges from 99 per cent at 19 per cent by volumeoxygen concentration in the inlet air to 98 per cent at 15 per centoxygen concentration.

The present combustor is also characterized by ease of ignition,stability of combustion over wide fuel feed ranges and lack of smoke.

The present apparatus is capable of burning any type of fluid fuelincluding gaseous fuels, kerosene, the various fuel oils, includingBunker C oil, alcohol, and other similar organic fuels and powderedcoal.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combustion apparatus for burning fluid fuel, a liner ofsubstantially circular cross-section closed at one end and open at theother end for the discharge of hot combustion gases, means forintroducing fuel into said liner adjacent the closed end thereof, meansfor igniting the fuel, means for cooling the inner wall of said linercomprising a plurality of axially disposed slots in said liner extendingfrom the fuel introducing means to nearly its discharge end, each ofsaid slots having associated therewith deflecting means for deflectingair entering the slots circumferentially over the inner surface of theliner, said deflecting means comprising a plurality of T-shaped membersmounted in inverse fashion in said slots and in end-to-end spacedrelationship to compensate for relative axial expansion between theliner and said deflecting means, the distance between the uprightportion of the defleeting means and the edge of the slots being 0.014 to0.03 that of the liner diameter and the distance between thehorizontally disposed portion of the deflecting means and inner surfaceof the liner being 0.003 to 0.01 that of the liner diameter.

2. In combustion apparatus for burning fluid fuel, a liner ofsubstantially circular cross-sec tion closed at one end and open at theother end for the discharge of hot combustion gases, means forintroducing fuel into said liner adjacent the closed end thereof, meansfor igniting the fuel, means for cooling the inner wall of said linercomprising a plurality of axially disposed slots in said liner extendingfrom the fuel introducing means to nearly its discharge end, each ofsaid slots having associated therewith deflecting means for deflectingair entering the slots circumferentially over the inner surface of theliner, said deflecting means comprising a plurality of T-shaped membersmounted in inverse fashion in said slots and in end-to-end spacedrelationship to compensate for relative axial expansion between theliner and said deflecting means, the

distance between the upright portion of the defleeting means and theedge of the slots being 0.007 that of the liner diameter and thedistance between the horizontally disposed portion of the deflectingmeans and the inner surface of the liner being about 0.0055 that of theliner diameter.

3. Combustion apparatus for burning fluid fuel comprising a liner ofsubstantially circular cross-section closed at one end and open at theother end for the discharge of hot combustion gases, means forintroducing fluid fuel into said liner adjacent the closed end thereof,means for igniting the fuel, means for introducing combustion andcooling air into said liner comprising from five to seven axiallydisposed equidistant slots in said liner extending from near the fuelintroducing means to nearly its discharge end, said slots havingassociated therewith means for deflecting air entering said slotscircumferentially over the inner surface of said liner, said deflectingmeans comprising T-shaped members mounted in inverse fashion in saidslots with the vertical portion extending upward through said slots inspaced relationship with the edges of said slots, the horizontal portionof said member forming a restricted passage with the inner surface ofsaid liner.

ROY W. ABBOTT.

588,086 Great Britain May 14, 1947

